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设集合A={x|x是小于6的正整数},B={x|(x-1)(x-2)=0},C={a,a2+1},
(Ⅰ)求A∩B,A∪B;
(Ⅱ)若B⊆C,且C⊆B,求实数a的值.
最常见的卵巢肿瘤是
A.浆液性囊腺瘤B.粘液性囊腺瘤C.成熟畸胎瘤D.内胚窦瘤E.纤维瘤